Co-nitration of 1,2,4-butanetriol and glycerin

ABSTRACT

A process for preparing an energetic mixture of 1,2,4-butanetroil  trinitr and nitroglycerin by forming a polyol mixture of 1,2,4-butanetriol and glycerin, and then nitrating the polyol mixture with a mixture of nitric and sulfuric acids.

BACKGROUND OF THE INVENTION

This invention relates to nitrate esters and more particularly tomethods of co-nitrating polyols to produce nitrate ester mixtures.

Mixtures of 1,2,4-butanetriol trinitrate and nitroglycerin are useful asenergetic components in explosives and gun propellants. Normally,1,2,4-butanetriol and glycerin are nitrated separately to form1,2,4-butanetriol trinitrate and nitroglycerin which are then blendedtogether in the desired proportions. This requires that one of thenitrate esters be stored while the other is being made. This storage isundesirable because either nitroglycerin or 1,2,4-butanetriol trinitrateis more sensitive to impact than a blended mixture of the two. Moreover,fume-offs frequently occur during the nitration of 1,2,4-butanetriolalone. It would be desirable to provide a method of reducing oreliminating these problems.

SUMMARY OF THE INVENTION

Accordingly, an object of this invention is to provide a new method ofproducing mixtures of 1,2,4-butanetriol trinitrate and nitroglycerin.

Another object of this invention is to provide a safer method ofproducing mixtures of 1,2,4-butanetriol trinitrate and nitroglycerin.

A further object of this invention is to avoid fume-offs during thepreparation of mixtures of 1,2,4-butanetriol trinitrate andnitroglycerin.

These and other objects of this invention are accomplished by providinga process for preparing an energetic binary mixture of 1,2,4-butanetrioltrinitrate and nitroglycerin by:

a. forming a binary polyol mixture of from about 40 to about 60 weightpercent of 1,2,4-butanetriol with the remainder of the polyol mixturebeing glycerin;

b. nitrating the polyol mixture with a mixed acid of from 30 to 60weight percent of nitric acid with the remainder of the mixed acid beingsulfuric acid; and

c. isolating the product mixture of 1,2,4-butanetriol trinitrate andnitroglycerin.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

It is critical that the 1,2,4-butanetriol, HOCH₂ CH(OH)CH₂ CH₂ OH, andglycerin, HOCH₂ CH(OH)CH₂ OH, starting materials be thoroughly mixedprior to the nitration step. In this way fuming off (of nitric acid),which frequently occurs in the normal nitration of 1,2,4-butanetriol, isavoided. Preferably from about 40 to about 60 and more preferably from50 to 55 weight percent of 1,2,4-butanetriol is used, with glycerinbeing the remainder of the polyol mixture.

A mixed acid containing from 30 to 60 weight percent of nitric acid withthe remainder being sulfuric acid is used as the nitrating agent. A morepreferred mixed acid will contain from 38 to 42 weight percent of nitricacid with the remainder being sulfuric acid.

The amount of mixed acid used will preferably provide an excess of from30 to 50 percent of nitric acid based on the stoichiometric amountcalculated for the complete conversion of 1,2,4-butanetriol and glycerinto 1,2,4-butanetriol trinitrate g and nitroglycerin. More preferably anexcess of from 40 to 44 percent of nitric acid is used.

Preferably the polyol mixture is fed into the mixed acid with vigorousagitation (e.g., stirring) of the mixed acid to prevent hot spots.Agitation of the reaction mixture is continued during the nitrationstep. The nitration reaction is exothermic and conventional methods suchas rate of polyol feed and external cooling are used to control thereaction temperature. Preferably the reaction temperature is kept in therange of from 5° C. to 20° C. Below 5° C. certain reactants may freezeand separate from the reaction mixture. Temperatures above 20° C. mayresult in the decompostion of the products.

The product 1,2,4-butanetriol trinitrate/nitroglycerin mixture separatesas a clear oil from the spent acid phase. There is no stable oil/wateremulsion formed. This contrasts with the nitration of glycerin alone inwhich some stable emulsion of nitroglycerin and water is usually formed.

As illustrated in the examples, the product 1,2,4-butanetrioltrinitrate/nitroglycerin oil mixture is washed first with a weak aqueousbase and then with water to remove traces of the acids.

To more clearly illustrate this invention, the following examples arepresented. It should be understood, however, that these examples arepresented merely as a means of illustration and are not intended tolimit the scope of the invention in any way.

EXAMPLE 1

46.6 grams of a binary solution of 53.1 weight percent of1,2,4-butanetriol (96 percent pure) and 46.9 weight percent of glycerinat 41° C. was pumped into 300 grams of mixed acid (38.1 weight percentof nitric acid and 58.8 weight percent of sulfuric acid) at 15±1° C.This is a 43 percent excess of nitric acid. During the nitration themixture was agitated with a high-speed, high-shear mixer. During thenitration the change in redox was 80 mv. (A sample of this1,2,4-butanetriol nitrated by itself had a change in redox of 130 mv.)The nitration mixture was drowned in 1000 grams of 6° C. water with a18° C. temperature rise. The calculated spent acid analysis was:

    ______________________________________                                        % Nitric Acid       11.8                                                      % Sulfuric Acid     71.8                                                      % Oxides            0.5                                                       % Water assuming 1% NG                                                                            13.9                                                      and 1% BTTN                                                                   H.sub.2 O/H.sub.2 SO.sub.4 Mole Ratio                                                             1.05                                                      ______________________________________                                    

The 1,2,4-butanetriol trinitrate (BTTN)/nitroglycerin (NG) mixture at35° to 40° C. was washed four times with 300 ml of 13 percent sodiumcarbonate and 3 times with water. Each wash was agitated for 15 minuteswith the high-speed, high-shear agitator. The results of the BTTN-NGanalysis are:

    ______________________________________                                        % BTTN         52.1                                                           % NG           46.9                                                           KI heat test min                                                                             18       10 min minimum                                        % water        0.1                                                            % N            17.9                                                           pH             Neutral                                                        ______________________________________                                    

EXAMPLE 2

The same as Example 1 except that a binary mixture of 52.07 weightpercent of 1,2,4-butanetriol (99.8 percent pure) and 47.93 weightpercent of glycerin was pumped into the mixed acid at a rate of 3.3grams per minute. The change in redox was 49 mv. (A sample of this1,2,4-butanetriol nitrated by itself had a change of redox of 58 mv.)The 1,2,4-butanetriol trinitrate (BTTN)/nitroglycerin (NG) mixture wasseparated from the spent acid. The results of the spent acid analysiswere:

    ______________________________________                                        % Nitric Acid       9.16                                                      % Sulfuric Acid     75.68                                                     % Oxide             0.64                                                      % Water (calculated)                                                                              11.6                                                      H.sub.2 O/H.sub.2 SO.sub.4 Mole Ratio                                                             0.86                                                      ______________________________________                                    

The results of BTTN-NG analysis were:

    ______________________________________                                               KI heat test                                                                          8.7          min                                                      % BTTN  50.9                                                                  % NG    49.1                                                           ______________________________________                                    

To those skilled in the art, many modifications and variations of thepresent invention are possible in light of the above teachings. It istherefore to be understood that the present invention can be practicedotherwise than as specifically described herein and still be within thescope of the appended claims.

What is claimed is:
 1. A process for preparing an energetic binarymixture of 1,2,4-butanetriol trinitrate and nitroglycerin comprising:a.forming a binary polyol mixture consisting essentially of from about 40to about 60 weight percent of 1,2,4-butanetriol with the remainder ofthe polyol mixture being glycerin; b. nitrating the polyol mixture witha mixed acid consisting essentially of from 30 to 60 weight percent ofnitric acid with the remainder of the mixed acid being sulfuric acid;and c. isolating the product mixture of 1,2,4-butanetriol trinitrate andnitroglycerin.
 2. The process of claim 1 wherein the binary polyolmixture consists essentially of from 50 to 55 weight percent of1,2,4-butanetriol with the remainder of the polyol mixture beingglycerin.
 3. The process of claim 1 wherein the nitration temperature ismaintained in the range of from 5° C. to 20° C. during step (b).
 4. Theprocess of claim 1 wherein the mixed acid consists essentially of from38 to 42 weight percent of nitric acid with the remainder of the mixedacid being sulfuric acid.
 5. The process of claim 1 wherein the amountof mixed acid used in step (b) provides a 30 to 50 percent excess ofnitric acid over the stoichiometric amount calculated for the completenitration of the 1,2,4-butanetriol and glycerin.
 6. The process of claim5 wherein the amount of mixed acid used in step (b) provides a 40 to 44percent excess of nitric acid over the stoichiometric amount calculatedfor the complete nitration of the 1,2,4-butanetriol and glycerin.